import { mkdir, rename, stat, unlink, writeFile } from 'node:fs/promises'
import path from 'node:path'
import { inferImageExtensionFromDataUrl, normalizeAssetBaseName } from '../helpers.js'
import { requireAdminAuth } from '../auth.js'
import { UPLOADS_DIR } from '../config.js'
import { isR2Configured, uploadToR2, deleteFromR2, copyInR2 } from '../r2.js'
import { state } from '../state.js'
import {
  listUploadedAssets,
  readUploadsMetadata,
  writeUploadsMetadata,
  getUserNotesFilePath,
  loadUserProgress,
  queueStudyUsersWrite,
} from '../data.js'
import {
  hashStudyPassword,
  getStudyCatalog,
  normalizeStudySlug,
  isEnrollableStudySlug,
  makeUnsubUrl,
  invalidateAllStudySessions,
} from '../study-helpers.js'
import { sendStudyReengagementEmail, sendStudyPasswordChangedEmail } from '../email.js'

const ALLOWED_FOLDERS = ['uploads', 'images', 'guides', 'finished']

function isSafeFilename(filename) {
  return typeof filename === 'string' && filename.length > 0 && !filename.includes('/') && !filename.includes('\\') && !filename.includes('..')
}

export function register(app) {
  app.get('/api/admin-assets', requireAdminAuth, async (_req, res) => {
    try {
      const assets = await listUploadedAssets()
      const haystack = JSON.stringify(state.cachedDraftSiteContent ?? {}) + JSON.stringify(state.cachedSiteContent ?? {})
      const withUsage = assets.map(asset => ({
        ...asset,
        usedIn: asset.url ? haystack.split(asset.url).length - 1 : 0,
      }))
      res.json({ assets: withUsage })
    } catch {
      res.status(500).json({ message: 'Could not list uploaded assets.' })
    }
  })

  app.post('/api/admin-assets', requireAdminAuth, async (req, res) => {
    try {
      const filename = typeof req.body?.filename === 'string' ? req.body.filename : ''
      const dataUrl = typeof req.body?.dataUrl === 'string' ? req.body.dataUrl : ''
      const rawFolder = typeof req.body?.folder === 'string' ? req.body.folder : 'uploads'
      const rawStorage = typeof req.body?.storage === 'string' ? req.body.storage : 'r2'
      const ext = inferImageExtensionFromDataUrl(dataUrl)

      const folder = ALLOWED_FOLDERS.includes(rawFolder) ? rawFolder : 'uploads'
      const useLocal = rawStorage === 'local' || !isR2Configured()

      if (!ext) {
        res.status(400).json({ message: 'Upload must be a PNG, JPG, WEBP, GIF, PDF, DOC, or DOCX data URL.' })
        return
      }

      const base64 = dataUrl.split(',')[1] ?? ''
      const buffer = Buffer.from(base64, 'base64')
      if (buffer.length === 0 || buffer.length > (8 * 1024 * 1024)) {
        res.status(400).json({ message: 'Upload must be between 1 byte and 8MB.' })
        return
      }

      const baseName = normalizeAssetBaseName(filename.replace(/\.[a-z0-9]+$/i, ''))
      const finalName = `${baseName}-${Date.now()}${ext}`

      let url
      if (useLocal) {
        await mkdir(UPLOADS_DIR, { recursive: true })
        await writeFile(path.join(UPLOADS_DIR, finalName), buffer)
        url = `/uploads/${finalName}`
      } else {
        const contentType = dataUrl.match(/^data:([^;]+);base64,/)?.[1] ?? 'application/octet-stream'
        url = await uploadToR2(buffer, `${folder}/${finalName}`, contentType)
      }

      const metadata = await readUploadsMetadata()
      metadata[finalName] = { tags: [], url, folder: useLocal ? 'local' : folder }
      await writeUploadsMetadata(metadata)

      res.json({ ok: true, asset: { filename: finalName, url, folder: useLocal ? 'local' : folder, storage: useLocal ? 'local' : 'r2' } })
    } catch (err) {
      console.error('[admin-assets] upload failed:', err)
      res.status(500).json({ message: 'Upload failed.' })
    }
  })

  app.patch('/api/admin-assets/:filename', requireAdminAuth, async (req, res) => {
    try {
      const { filename } = req.params
      if (!isSafeFilename(filename)) {
        res.status(400).json({ message: 'Invalid filename.' })
        return
      }

      const metadata = await readUploadsMetadata()
      const current = (await listUploadedAssets()).find(a => a.filename === filename)
      if (!current) {
        res.status(404).json({ message: 'Asset not found.' })
        return
      }

      const entry = metadata[filename]
      let tags = Array.isArray(entry)
        ? entry
        : Array.isArray(entry?.tags) ? entry.tags : []
      if (Array.isArray(req.body?.tags)) {
        tags = req.body.tags.filter(tag => typeof tag === 'string').map(tag => tag.trim()).filter(Boolean)
      }

      let newFilename = filename
      let newUrl = current.url
      let newFolder = current.folder
      const ext = path.extname(filename)

      const wantsRename = typeof req.body?.newName === 'string' && req.body.newName.trim()
      const wantsMove = typeof req.body?.folder === 'string' && req.body.folder !== current.folder

      if (wantsRename) {
        const base = normalizeAssetBaseName(req.body.newName.trim().replace(/\.[a-z0-9]+$/i, ''))
        newFilename = `${base}${ext}`
      }
      if (wantsMove) {
        if (current.storage !== 'r2' || !ALLOWED_FOLDERS.includes(req.body.folder)) {
          res.status(400).json({ message: 'Only R2 assets can be moved, to uploads, images, guides, or finished.' })
          return
        }
        newFolder = req.body.folder
      }

      if (newFilename !== filename || newFolder !== current.folder) {
        if (newFilename !== filename) {
          const taken = (await listUploadedAssets()).some(a => a.filename === newFilename && a.folder === newFolder)
          if (taken) {
            res.status(409).json({ message: `A file named ${newFilename} already exists there.` })
            return
          }
        }
        if (current.storage === 'r2') {
          const newKey = `${newFolder}/${newFilename}`
          newUrl = await copyInR2(current.key, newKey)
          await deleteFromR2(current.key)
        } else {
          await rename(path.join(UPLOADS_DIR, filename), path.join(UPLOADS_DIR, newFilename))
          newUrl = `/uploads/${newFilename}`
        }
        delete metadata[filename]
      }

      metadata[newFilename] = { tags, url: newUrl, folder: current.storage === 'r2' ? newFolder : 'local' }
      await writeUploadsMetadata(metadata)

      res.json({ ok: true, tags, filename: newFilename, url: newUrl, folder: newFolder, oldUrl: current.url })
    } catch (err) {
      console.error('[admin-assets] update failed:', err)
      res.status(500).json({ message: 'Could not update asset.' })
    }
  })

  app.delete('/api/admin-assets/:filename', requireAdminAuth, async (req, res) => {
    try {
      const { filename } = req.params
      if (!isSafeFilename(filename)) {
        res.status(400).json({ message: 'Invalid filename.' })
        return
      }

      // Optional ?folder= disambiguates identical filenames in different R2 folders.
      const folder = typeof req.query.folder === 'string' ? req.query.folder : null
      const matches = (await listUploadedAssets()).filter(a => a.filename === filename && (!folder || a.folder === folder))
      const target = matches[0]
      if (!target) {
        res.status(404).json({ message: 'Asset not found.' })
        return
      }

      if (target.storage === 'r2') {
        await deleteFromR2(target.key)
      } else {
        await unlink(path.join(UPLOADS_DIR, filename)).catch(() => {})
      }

      const metadata = await readUploadsMetadata()
      delete metadata[filename]
      await writeUploadsMetadata(metadata)
      res.json({ ok: true })
    } catch (err) {
      console.error('[admin-assets] delete failed:', err)
      res.status(500).json({ message: 'Delete failed.' })
    }
  })

  // ── Admin: Study User Management ─────────────────────────────────────────

  app.get('/api/admin/study-users', requireAdminAuth, async (req, res) => {
    const catalog = getStudyCatalog()
    const users = await Promise.all(state.studyUsers.map(async user => {
      let noteCount = 0
      try {
        const { readFile } = await import('node:fs/promises')
        const notesRaw = await readFile(getUserNotesFilePath(user.id), 'utf8').catch(() => '{}')
        const notes = JSON.parse(notesRaw)
        noteCount = Object.values(notes).filter(n => typeof n === 'string' && n.trim()).length
      } catch { /* ignore */ }

      let progressByStudy = {}
      try {
        const prog = await loadUserProgress(user.id)
        for (const [slug, data] of Object.entries(prog.byStudy)) {
          progressByStudy[slug] = { completedLessons: (data.completedSectionIds ?? []).length }
        }
      } catch { /* ignore */ }

      const enrolledStudies = (user.enrolledStudySlugs ?? []).map(slug => {
        const study = catalog.find(s => s.slug === slug)
        return study
          ? { slug, title: study.title, completedLessons: progressByStudy[slug]?.completedLessons ?? 0 }
          : { slug, title: slug, completedLessons: 0 }
      })

      return {
        id: user.id,
        username: user.username,
        displayName: user.displayName ?? '',
        createdAt: user.createdAt ?? null,
        lastLoginAt: user.lastLoginAt ?? null,
        enrolledStudies,
        noteCount,
        subscribeNewsletter: user.subscribeNewsletter !== false,
        studyRemindersEnabled: user.studyRemindersEnabled === true,
        reminderFrequency: user.reminderFrequency ?? 'immediate',
        remindersPausedUntil: user.remindersPausedUntil ?? null,
        currentStreak: user.currentStreak ?? 0,
        longestStreak: user.longestStreak ?? 0,
        reengagementSentAt: user.reengagementSentAt ?? {},
        adminShortcut: user.adminShortcut === true,
      }
    }))

    res.json({ users })
  })

  app.post('/api/admin/study-users/:id/send-reengagement', requireAdminAuth, async (req, res) => {
    const user = state.studyUsers.find(u => u.id === req.params.id)
    if (!user) { res.status(404).json({ message: 'User not found.' }); return }

    const tier = req.body?.tier
    if (tier !== 't1' && tier !== 't2' && tier !== 't3') {
      res.status(400).json({ message: 'tier must be t1, t2, or t3.' }); return
    }

    const studies = Array.isArray(state.cachedSiteContent?.studies) ? state.cachedSiteContent.studies : []
    const enrolledStudySlugs = Array.isArray(user.enrolledStudySlugs) ? user.enrolledStudySlugs : []
    const enrolledStudies = enrolledStudySlugs
      .map(slug => studies.find(s => normalizeStudySlug(s?.slug) === slug))
      .filter(Boolean)

    if (enrolledStudies.length === 0) { res.status(400).json({ message: 'User has no enrolled studies.' }); return }

    const firstStudy = enrolledStudies[0]
    const studyTitle = enrolledStudies.length === 1 ? firstStudy.title : null
    const canonical = state.cachedSiteContent?.seo?.canonicalUrl || 'https://versebyversewithnate.us/'
    const base = canonical.endsWith('/') ? canonical.slice(0, -1) : canonical
    const studyUrl = enrolledStudies.length === 1 ? `${base}/study/${firstStudy.slug}` : `${base}/study`
    const unsubUrl = makeUnsubUrl(user.id)

    try {
      await sendStudyReengagementEmail(user.username, user.displayName || user.username, studyTitle, studyUrl, tier, unsubUrl)
      res.json({ ok: true })
    } catch (err) {
      console.error(`[admin] manual reengagement send failed for ${user.username}:`, err)
      res.status(500).json({ message: 'Failed to send email.' })
    }
  })

  app.patch('/api/admin/study-users/:id', requireAdminAuth, (req, res) => {
    const user = state.studyUsers.find(u => u.id === req.params.id)
    if (!user) { res.status(404).json({ message: 'User not found.' }); return }

    const { displayName, newPassword, addEnrollment, removeEnrollment, adminShortcut } = req.body ?? {}

    if (typeof displayName === 'string') {
      user.displayName = displayName.trim().slice(0, 80)
    }

    if (typeof adminShortcut === 'boolean') {
      user.adminShortcut = adminShortcut
    }

    if (typeof newPassword === 'string') {
      if (newPassword.length < 8 || newPassword.length > 200) {
        res.status(400).json({ message: 'Password must be 8–200 characters.' }); return
      }
      user.passwordHash = hashStudyPassword(newPassword)
      invalidateAllStudySessions(user.id)
      sendStudyPasswordChangedEmail(user.username, user.displayName || user.username)
        .catch(err => console.error('[admin] password-changed email error:', err))
    }

    if (typeof addEnrollment === 'string' && addEnrollment.trim()) {
      const slug = normalizeStudySlug(addEnrollment)
      if (!slug || !isEnrollableStudySlug(slug)) {
        res.status(400).json({ message: `Unknown study slug: ${addEnrollment.trim()}` }); return
      }
      if (!Array.isArray(user.enrolledStudySlugs)) user.enrolledStudySlugs = []
      if (!user.enrolledStudySlugs.includes(slug)) user.enrolledStudySlugs.push(slug)
    }

    if (typeof removeEnrollment === 'string' && removeEnrollment.trim()) {
      const slug = removeEnrollment.trim()
      user.enrolledStudySlugs = (user.enrolledStudySlugs ?? []).filter(s => s !== slug)
    }

    user.updatedAt = new Date().toISOString()
    queueStudyUsersWrite()
    res.json({ ok: true, displayName: user.displayName, enrolledStudySlugs: user.enrolledStudySlugs, adminShortcut: user.adminShortcut === true })
  })

  app.delete('/api/admin/study-users/:id', requireAdminAuth, async (req, res) => {
    const user = state.studyUsers.find(u => u.id === req.params.id)
    if (!user) { res.status(404).json({ message: 'User not found.' }); return }

    invalidateAllStudySessions(user.id)

    state.studyUsers = state.studyUsers.filter(u => u.id !== user.id)
    queueStudyUsersWrite()

    state.studyNotesCache.delete(user.id)
    try { await unlink(getUserNotesFilePath(user.id)) } catch { /* no notes file is fine */ }

    res.json({ ok: true })
  })
}